The Long Term Evolution (LTE) technology introduces the Orthogonal Frequency Division Multiplexing (OFDM) technology, of which one advantage is that the Inter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI) can be reduced via Cyclic Prefix (CP). In LTE R9, the PRS is introduced in order to measure the location of the receiving side, so that the receiving side can accurately measure the location of the receiving side by using the PRS. The PRS can be configured and transmitted in the Normal subframe and the Multiple Broadcast Single Frequency Network (MBSFN) subframe in the LTE radio frame. In one radio frame, if the PRS is configured in the Normal subframe and in the MBSFN subframe, the OFDM symbol CP length of the subframe where the PRS locates needs to be configured as the CP length of the subframe 0; if the PRS is only configured in the MBSFN subframe, the OFDM symbol CP of the subframe where the PRS locates needs to be configured as Extended CP.
In LTE Release 9 stage, an MBSFN domain and a Non-MSBFN domain can be configured in the MSBFN subframe, wherein the Non-MSBFN domain only can include former one OFDM symbol or two OFDM symbols in one subframe. The Physical Downlink Control Channel (PDCCH) of Release 8 and Release 9 can be transmitted in the Non-MSBFN domain of the MBSFN subframe, however, the MBSFN domain is not allowed to be configured as the Physical Downlink Shared Channel (PDSCH) of Release 8 and Release 9 for transmission. In the LTE-Advanced R10 stage, both of the Non-MBSFN domain and the MBSFN domain in the MBSFN subframe can be configured to transmit the PDCCH and PDSCH of Release 10. In addition, whether the PDSCH of Release 10 in the MBSFN subframe adopts the Normal CP or the Extended CP is not scheduled by an individual rule in the standard; it is described in the Release 10 36.814 that the PDSCH of Release 10 in the MBSFN subframe adopts the CP length of the subframe 0. So the solution finally adopted in the standard is that the CP of PDSCH in the MBSFN subframe is transmitted according to the CP length detected by the receiving side, namely, the receiving side uniformly transmits the PDSCH according to the CP length of the subframe 0, without identifying whether it is the Normal subframe or the MBSFN subframe.
The problem caused here is that if the PRS is only transmitted in the MBSFN subframe, and if the PDSCH of Release 10 is transmitted in the MBSFN subframe, the Extended CP needs to be transmitted in the MBSFN subframe at this time according to the requirements of the PRS, whereas the CP of the subframe 0 needs to be transmitted in the MBSFN subframe according to the requirements of the PDSCH of Release 10; if the CP of the subframe 0 is configured to be the Normal CP at this time, different CP lengths in this subframe may conflict with each other. The receiving side does not know the CP type adopted by the network side in this subframe, thus causing incorrect detection.
The Channel State Information Reference Signal (CSI-RS) and the Relay backhaul link have the same problem with the PDSCH, namely, referring to the CP length ambiguity, so that the signals cannot be measured and accurately received.